This invention relates to methods of preventing and treating infections. More specifically, it relates to the use of biodegradable implants which contain an antibiotic and provide a sustained release of that antibiotic when they are implanted into surgical voids.
Virtually all surgical procedures create some type of void or dead space within the patient's body. This is particularly true in the case of surgery to remedy a localized infection. The area where the infection is focused, an area of relative tissue ischemia, must be debrided and filled in. Further, antibiotics must be administered to prevent recurrence of infection in the void.
One example is chronic bone infection (osteomyelitis). The standard therapy includes debridement and sequestrectomy of infected, dead bone, followed by several weeks of intravenous antibiotics. Unfortunately this treatment has several drawbacks. The multiple doses of antibiotics that are needed can become quite expensive. Also, the intravenous route of administration does not allow the antibiotic to be specifically directed to the location of the infection. Further, intravenous administration of antibiotics requires an operation for placement of a catheter, which can lead to serious complications.
One improvement to this procedure is the use of polymethylmethacrylate (PMMA) beads that contain antibiotics. Such beads are placed in surgical voids and thereby fill the voids, as well as providing local bactericidal levels of antibiotic. However, even these PMMA beads have disadvantages. First, they usually can only provide bactericidal levels of antibiotic for about two weeks, so parenteral antibiotic must be given also. Second, the PMMA beads must eventually be removed surgically, resulting in further trauma to the patient's body. Third, the beads provide no flexibility in the release rate of the antibiotic. This is important, because antibiotics are needed for longer periods to treat slow healing, ischemic wounds, such as in bone, than for more rapidly-healing, well vascularized wounds, such as in muscle.
Also, it is common for one type of bacteria to be present initially in a surgical void and, as treatment with a first antibiotic eliminates that organism, for a second type of bacteria to become present. Often, the second type of bacteria cannot be effectively treated with the same antibiotic as the first type of bacteria. Therefore, an implant that releases a single antibiotic, or releases multiple antibiotics at about the same rate, will not be fully effective in such a situation.
A long-standing need exists for improved methods for preventing and treating infections in voids created by surgery.